On Thu, Aug 13, 2026 at 11:30:32PM +0800, Ruoyu Wang wrote:
> check_locality() treats every nonzero transport return as success. SPI
> errors remain negative, while the I2C path can convert a negative write
> error through its byte-sized status variable. Either result is nonzero
> even though the TPM_ACCESS byte can remain unwritten, so indeterminate
> ACTIVE_LOCALITY and VALID bits can falsely report an active locality.
>
> Require recv() to return exactly the requested byte before examining
> TPM_ACCESS. Transport errors and short reads now report an inactive
> locality, while successful reads retain the existing behavior.
>
> This issue was found by a static analysis checker and confirmed by manual
> source review.
>
> Fixes: 251a7b08213a ("TPM: STMicroelectronics ST33 I2C KERNEL 3.x")
> Signed-off-by: Ruoyu Wang <[email protected]>
> ---
> drivers/char/tpm/st33zp24/st33zp24.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/tpm/st33zp24/st33zp24.c
> b/drivers/char/tpm/st33zp24/st33zp24.c
> index 898e8d01d26698..0e2deff94c3672 100644
> --- a/drivers/char/tpm/st33zp24/st33zp24.c
> +++ b/drivers/char/tpm/st33zp24/st33zp24.c
> @@ -106,10 +106,10 @@ static bool check_locality(struct tpm_chip *chip)
> {
> struct st33zp24_dev *tpm_dev = dev_get_drvdata(&chip->dev);
> u8 data;
> - u8 status;
> + int status;
>
> status = tpm_dev->ops->recv(tpm_dev->phy_id, TPM_ACCESS, &data, 1);
> - if (status && (data &
> + if (status == 1 && (data &
> (TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID)) ==
> (TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID))
> return true;
> --
> 2.51.0
>
Reviewed-by: Jarkko Sakkinen <[email protected]>
BR, Jarkko
